WENNER

For a catalyst packed reactor, a rate equation was found by Wenner and Dybdal (Chem. Eng. Frog., 44, 275-286 [1948]) ... 

Fig. 3-14 Circuit of a measuring instrument for determining the apparent soil resistance by the Wenner method.

The Wenner method is chiefly used to determine the grounding resistance along the pipeline track and the installation positions for cathodic structures. Local limited soil resistivity is most clearly determined from the grounding resistance of an inserted Shephard rod (see Fig. 3-18). Soil stratification can be recognized from the apparent specific soil resistivity, p, by the Wenner method, if a is varied. 

Since the Wenner formula [Eq. (24-41)] was deduced for hemispherical electrodes, measuring errors appear for spike electrodes. To avoid errors in excess of 5%, the depth of penetration must be less than a 5. Soil resistivity increases greatly under frost conditions. While electrodes can be driven through thin layers of frost, soil resistivity measurements deeper than 20 cm in frozen ground are virtually impossible. 

Since the Wenner rod is mechanically somewhat delicate, it is only used in loose soils or in bore holes. For all measuring rods, the specific soil resistivity is equal to the product of the measured ac resistance and the shape factor Fq, which is determined empirically. 

Measurement of resistivity The most usual method of measuring soil resistivity is by the four-electrode Wenner method. Figure 10.48 indicates the basic circuit. The mean resistivity is given by... 

Wenner method. Normally Ct, Cz and Pu Pt are stetl rods, bm for high -accuracy Cu/CuS04 electrodes should he used for Pu Pi... 

The ethylbenzene dehydrogenation catalyst of Example 3.1 has a first-order rate constant of 3.752 s at 700°C. How does this compare with the catalyst used by Wenner and Dybdal. They reported... 

This research was supported by a grant from the Wenner-Gren Foundation for Anthropological Research to N.J. van der Merwe, and by Harvard University. We thank Christine White and the editors for their useful comments on an earlier draft of this paper, and Mrs. Aijelia Martinez and her dog, Blackie, for samples of modem Mr. 

We gratefully acknowledge support from the Wenner-Gren Foundation for Anthropological Research, The L.S.B. Leakey Foundation and the Social Sciences and Humanities Research Council of Canada who provided financial support for the seminar. Our institutions, the Department of Archaeology, University of Calgary and the Department of Anthropology, University of Illinois, also made contributions. Finally, we thank the contributors for their patience and their hard work. 

Oechel, W.D. Collins, N.J. (1973). Seasonal patterns of CO2 exchange in bryo-phytes at Barrow, Alaska. In Primary Production and Production Processes, ed. L.C. Bliss and F.E. Wielogolaski, pp. 197-203. Stockholm Wenner-Gren Center. 

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